Urban Sustainability: Comparative Value of Building-Top Apartments.

Abstract

This paper discusses the ecological performance of constructing new apartments on top of existing buildings. The emerging architectural typology of ‘building-top apartments’ in Wellington is discussed as a more ‘sustainable’ solution to urban apartments compared with conventional ‘demolished-site’ development. Apartments built on top of existing buildings are a typology that averts demolishing the host building thereby avoiding waste and improving lifecycle performance. It can be built more economically because it does not require excavation and footings. It contributes to urban population intensification thereby supporting city social and cultural vitality and economic development. It accommodates many people who walk to work thereby reducing motor vehicle congestion and pollution as well as potentially contributing to public health through better fitness. It supports higher numbers of people in the city as casual observers and thereby potentially contributes to reduction in crime. By accommodating a significant proportion of the city’s population growth building-top apartments comparatively help reduce land subdivision on the city’s boundaries which consume energy and resources at a higher rate. Wellington has an emerging urban architectural typology that can be shown to be contributing to city sustainability in terms of having less impact on the environment than conventional development while also contributing to better economic performance and to social and cultural endeavours. The paper scopes across a range of matters while focusing on building sustainability, specifically site development, life cycle assessment, cost of demolition, cost of footings and foundations, construction waste and embodied energy and CO2 emissions.

Building-top apartments in Wellington are a breeding ground for new ideas and are seen as an important vehicle for city renewal with lessons that may be transferable to other cities.